Before I comment on this I want to state that Dr. Moller is, without a doubt, a brilliant man and an extraordinary aerodynamic engineer. Certainly, he's far beyond my expertise. That said, he and those with whom he works have a long history of making claims that are never fulfilled. A good place to start reading about this aspect is at Wikipedia's Skycar page.
Now, Mr. Calkins is stating that the Skycar will cruise using 120 horsepower. The Skycar specifications page states that the cruise speed at 25,000 feet is 305 m.p.h. and that "max mileage" is greater than 20 m.p.g. It's not stated what airspeed is utilized to achieve this mileage. It may be very much lower than 305 m.p.h. In my airplane, the maximum range airspeed (that is, the airspeed at which I can achieve the greatest number of miles per gallon) is about 24% lower than normal cruise speed. Interestingly, on another page the claim is that "